1. Field of the Invention
The invention relates to an air and fuel injection apparatus for the combustion chamber of a gas turbine engine and more particularly to such an injection apparatus having an improved air admission pattern for reducing smoke generation and maintaining the face of a fuel oil nozzle relatively clean of carbon deposits.
2. Description of the Prior Art
Fuel injectors for admitting fuel oil to a combustion chamber of a gas turbine engine generally include a nozzle comprising a central orifice through which the oil is introduced and atomized in a conical pattern surrounded by air injecting apertures which mix air with the fuel and carry it into the primary combustion zone of the combustion chamber where it is mixed with additional combustion air and combusted to provide the hot motive gases for driving the turbine rotor.
Such fuel atomization and subsequent mixing with combustion air produces inhomogeneities in the air-fuel mixture such that even though sufficient air is introduced to the combustion zone to provide complete combustion, fuel rich pockets occur resulting in incompletely burned hydrocarbons which in turn result in smoke emissions. This smoke can be subsequently partially diluted by mixing the combustion products with dilution and cooling air downstream of the primary zone, but a better means is to eliminate the fuel rich pockets by a more vigorous mixing of the air with the fuel while maintaining the stability of the flame in the combustion zone.
In the present fuel nozzle, merely increasing the airflow into the primary combustion zone reduces the flame stability and increases the minimum outlet temperature at which blow-out occurs. Thus, the air-fuel mixture pattern must be altered in a manner such that the fuel rich pockets are eliminated but the flame remains stable even at low fuel flows.